The invention relates generally to vacuum separators having vacuum filter discs or assemblies adapted for selective and periodic connection to a vacuum source and an air pressure source, and the filter discs being supported for rotation through a slurry for effecting separation of solid materials from the slurry. More particularly, the invention relates to an improved means for connecting the filter sectors of the filter discs to the air pressure source.
Prior art vacuum separators have included a rotating cylinder supporting a plurality of filter discs, each of the filter discs surrounding a portion of the cylinder and lying in a plane transverse to the cylinder axis. The filter discs are supported for rotation with the cylinder in such a manner that the filter discs are dipped into a slurry contained in a tank beneath the cylinder. The cylinder supports conduits which provide fluid communication between a vacuum source and the filter sectors of the filter discs whereby as the filter sectors move through the slurry, the slurry is drawn through the filters and solid particles suspended in the slurry may be caused to adhere to the filter. Means are further provided to selectively connect certain of the conduits and associated filter sectors to an air pressure source as the filter sectors reach a certain position in their rotational movement whereby air is blown through those conduits and through the filter sectors to cause the solid particles thereon to be blown away from the filter into a collecting means.
Frequently, a large number of filter discs are disposed in stacked parallel relation along the length of the cylinder and air pressure is simultaneously blown through one filter sector of each of those discs. To provide for efficient discharge of the solid particles from the surfaces of the filter sectors, the air pressure applied to the filter sectors should be maintained until all of the solid material coating the surface of the filter sectors is blown off. A premature reduction in air pressure results in those pores in the filter sectors which are initially blown clean transmitting airflow and the fine pores in the filter sectors are not blown out. This results in reduced efficiency of the vacuum separation process. Accordingly, it is critical that the air pressure applied to the filter sectors be maintained without reduction until all of the solid material covering the filter segments is discharged. As a result, prior art vacuum separators have commonly employed large air pressure tanks in an attempt to provide the required air pressure to the filter sectors for the necessary time period. However, even use of such large air pressure tanks has failed to provide a means for consistently and completely blowing the solid material off the filter sector surfaces.